JP2009030646A - Constant velocity joint and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a constant velocity joint maintaining a velocity stability characteristics over a long period of time and smoothly incorporating a cage in the outer ring, and also to provide an image forming apparatus. <P>SOLUTION: By setting the diameter A of a through hole 151a to be larger than the diameter B of a ball 152, the ball 152 can move in a radial direction within the through hole 151a. As a result, when the ball 152 abuts against the cup portion 141 of the outer ring 140 when inserting an insertion section 151 of the cage 150 in an annular space of the outer ring, the ball 152 moves toward the axial center, so that the insertion section 151 of the cage 150 is smoothly inserted in the annular space 144 of the outer ring 140. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a constant velocity joint and an image forming apparatus.

  Conventionally, a constant velocity joint is known as one of drive transmission mechanisms for transmitting rotational torque of a drive shaft of an automobile to an axle. The constant velocity joint can transmit a driving force between them in the rotational direction at a constant velocity while allowing a deviation angle between the driving shaft on the driving side and the driven shaft on the driven side that are aligned in the axial direction. . The constant velocity joint is a drive transmission mechanism that is widely used not only in automobiles but also in various industrial machines.

  As a constant velocity joint, for example, a triball joint as described in Patent Document 1 is generally known. The triball joint includes an outer ring and a cage that are aligned in the axial direction. The outer ring has an annular space that opens at one end, and outer grooves that are track grooves that extend in the axial direction and are arranged at intervals of 120 ° in the circumferential direction are formed on the outer wall surface of the annular space. . In addition, an inner groove serving as a track groove is formed on the inner wall surface of the annular space so as to face the outer groove while extending in the axial direction. On the other hand, the cage is formed such that ball holding holes are arranged at intervals of 120 ° in the circumferential direction on a hollow cylindrical peripheral wall inserted into the annular space of the outer ring. Holding the ball. The cage is inserted into the annular space of the outer ring so that these balls engage with the inner and outer grooves of the outer ring. In this state, when either the outer ring or the cage rotates on the driving side, the rotational force is transmitted to the other through a plurality of balls engaged with the inner and outer grooves.

  The conventional triball joint having such a configuration has a drawback that it is heavy because the outer ring and the cage are made of metal. In addition, there is a drawback that the operation sound becomes loud due to the friction between the ball and the track groove. Furthermore, grease is filled in the annular space of the outer ring for the purpose of smoothly rolling the ball. However, there is a concern about grease contamination to the surrounding environment due to leakage of this grease. As a result, it has been difficult to apply to office machines, audio equipment, medical equipment, household appliances, food manufacturing equipment, and the like.

  Patent Document 2 describes a triball joint in which an outer ring is formed of a synthetic resin (polyacetal resin) having a very small frictional resistance. By forming the outer ring with a resin material, the weight of the outer ring can be reduced as compared with the conventional configuration formed with a metal material. Further, since the frictional resistance is very small, the outer ring and the cage can be smoothly rotated without filling the annular space of the outer ring, and the operation sound can be reduced as compared with that made of metal. As a result, the triball joint can be applied to office machines, audio equipment, medical equipment, household appliances, food manufacturing equipment, and the like.

Japanese Patent Publication No. 52-34699 JP 2006-38204 A

  However, in the constant velocity joint described in Patent Document 2, when the fitting gap between the ball and the ball holding hole is zero when the ball is held in the ball holding hole, the constant velocity accuracy cannot be maintained for a long time. I understood it. This is because if the fitting gap between the ball and the ball holding hole is zero, the ball cannot rotate smoothly with respect to the ball holding hole. As a result, the sliding resistance between the track groove (inner groove and outer groove) and the ball increases, and the track groove (inner groove and outer groove) wears out early. When the worn portions of the track grooves (inner grooves and outer grooves) were observed, it was found that there were a portion where wear progressed earlier and a portion where wear progressed faster rather than being worn evenly in the axial direction. As described above, since the progress of wear differs in the axial direction of the groove, the track groove (inner groove and outer groove) is uneven, and this unevenness prevents the ball from sliding in the axial direction. It has been found that cannot be maintained over a long period of time.

  In addition, when the fitting gap between the ball and the ball holding hole is zero, the ball cannot smoothly move in the radial direction with respect to the holding hole. As a result, the insertion resistance when the ball held in the cage is inserted into the annular space of the outer ring may increase, and the cage and the outer ring may not be assembled smoothly. This will be specifically described below.

  When the cage is engaged with the outer ring when there is a radial shift between the ball and the track groove (outer groove and inner groove) due to errors in mounting the ball to the ball holding hole, etc. The ball contacts the opening end of the outer wall surface of the annular space of the outer ring or the opening end of the inner wall surface. At this time, if the ball cannot move smoothly in the radial direction with respect to the holding hole, the ball is moved in the radial direction unless the cage is pushed firmly to the outer ring side, and the ball and the track groove (outer groove and (Inner groove) and radial deviation are not corrected. As a result, the insertion resistance when the ball held in the cage is inserted into the annular space of the outer ring increases, and the cage cannot be smoothly assembled to the outer ring.

  The present invention has been made in view of the above problems, and the object of the present invention is to maintain a constant velocity over a long period of time, and a constant velocity joint capable of smoothly assembling the cage to the outer ring. An image forming apparatus is provided.

In order to achieve the above object, the invention of claim 1 has an annular space having one end opened, and a plurality of shafts formed at equal intervals in the circumferential direction on at least one of an outer wall surface and an inner wall surface of the annular space. An outer ring having a track groove extending in a direction, and a cage having a ball holding hole for holding a ball sliding along the track groove, and the outer ring and / or the cage is molded of a synthetic resin, With a part of the cage inserted into the annular space and the ball held by the cage engaged with the track groove, the rotational driving force of either the cage or the outer ring is interposed via the ball. In the constant velocity joint for transmitting to the other, the diameter of the ball holding hole is made larger than the diameter of the ball.
According to a second aspect of the present invention, in the constant velocity joint of the first aspect, the diameter of the ball holding hole is larger than the diameter of the ball by 5 [μm] or more and 50 [μm] or less. Is.
The invention of claim 3 is characterized in that, in the constant velocity joint of claim 1, the diameter of the ball holding hole is larger by 10 [μm] or more and 30 [μm] or less than the diameter of the ball. Is.
According to a fourth aspect of the present invention, there is provided a unit having a rotating body and detachable from the apparatus main body, a driven shaft provided in the unit for transmitting a driving force to the rotating body, and the apparatus main body. 4. An image forming apparatus comprising: a connecting means for connecting a driving shaft that receives a driving force from a drive source that is driven to rotate; and the constant velocity joint according to claim 1 as the connecting means. It is characterized by being used.

According to the first to fourth aspects of the present invention, since the hole diameter of the ball holding hole is larger than the diameter of the ball, the ball holding hole does not restrain the ball, and the ball holding hole inhibits the rotation of the ball. There is no need to do it. As a result, the ball can be smoothly rotated, and the track groove can be slid while the ball rotates during driving. As a result, it is possible to suppress wear of the track groove, and to prevent the track groove from being uneven due to wear. As a result, the ball can smoothly slide in the track groove over a long period of time, and constant velocity can be maintained over a long period of time. Further, the wear of the outer ring track groove is suppressed, and the durability of the constant velocity joint can be improved.
Further, the ball holding hole and the ball do not come into contact with each other, and the ball holding hole does not hinder the movement of the ball in the radial direction. Therefore, when the ball is inserted into the annular space between the track grooves, the phase of the ball and the track groove is shifted in the radial direction so that the ball is positioned at the opening end of the outer wall surface or the inner wall opening surface of the annular space. Even if it comes into contact, the ball smoothly moves in the radial direction. Accordingly, the radial phases of the balls and the grooves can be matched without strongly pushing the cage toward the outer ring, and the cage can be smoothly assembled to the outer ring.

Hereinafter, an embodiment of an electrophotographic printer (hereinafter simply referred to as a printer) will be described as an image forming apparatus to which the present invention is applied.
First, the basic configuration of the printer will be described. FIG. 1 is a schematic configuration diagram showing the printer. In the figure, the printer includes four process cartridges 1Y, C, M, and K for generating toner images of yellow, cyan, magenta, and black (hereinafter referred to as Y, C, M, and K). Yes. These use Y, C, M, and K toners of different colors as image forming substances for forming an image, but other than that, they have the same configuration and are replaced when the lifetime is reached. In the following description, since the process cartridges 1Y, 1C, 1M, and 1K have the same configuration, the reference symbols Y, C, M, and K for color classification are omitted.
As shown in FIG. 2, the process cartridge 1 contains a drum-shaped photosensitive member 2 as an image carrier, a drum cleaning unit 3, a charging unit 4, a developing unit 5, a lubricant application unit 6, and the like in a frame not shown. ing. The process cartridge 1 can be attached to and detached from the printer body, so that consumable parts can be replaced at a time.

  The charging unit 4 uniformly charges the surface of the photoreceptor 2 that is rotated clockwise in the drawing by a driving unit (not shown). In the figure, the charging roller 4a, which is a rotating member that is driven to rotate counterclockwise in the drawing while a charging bias is applied by a power source (not shown), is not in contact with the photosensitive member 2 to uniformly charge the photosensitive member 2. The non-contact charging roller type charging unit 4 is shown. As the charging unit 4, other than the above, a scorotron method, a corotron method, a contact roller method, or the like can be used.

As the charging bias applied to the contact type and non-contact type charging roller 4a, there are a type in which alternating current is superimposed on direct current, and a method in which only direct current is applied. The charging bias that superimposes the alternating current on the direct current in the contact type charging roller 4a is such that the surface potential of the charging roller 4a remains constant even if the resistance value of the charging roller 4a changes due to environmental changes by controlling the alternating current to a constant current. There is a merit that is not affected. However, the cost of the power supply device becomes high, and AC high frequency sound is a problem. On the other hand, in the non-contact charging roller 4a, the surface of the photosensitive member cannot be uniformly charged due to the influence of the gap fluctuation between the photosensitive member 2 and the charging roller 4a with the charging bias that superimposes the alternating current on the direct current. , The image is uneven. For this reason, a charging bias correcting means corresponding to the gap fluctuation is required.
The charging roller 4a can be driven by a method of rotating with the photosensitive member 2 or a method of obtaining a driving force from a driving source for driving the photosensitive member 2 through a gear or the like. In the case of a low-speed machine, a method of rotating with the photosensitive member 2 is generally used. The latter method is common for devices that require high speed and high image quality.

  In the figure, a charging roller cleaner 4b for cleaning the surface of the charging roller 4a is provided. Thereby, it is possible to prevent the photosensitive member 2 from being charged to the target potential due to dirt adhering to the charging roller 4a. As a result, abnormal images due to poor charging can be suppressed. The charging roller cleaner 4b is generally composed of melanin, and is configured to rotate with the charging roller 4a.

  The developing unit 5 as developing means has a first agent accommodating portion 5e in which a first conveying screw 5a is disposed. Further, it also has a second agent storage portion 5f in which a toner concentration sensor 5c composed of a magnetic permeability sensor, a second transport screw 5b, a developing roll 5g, a doctor blade 5d, and the like are disposed. In these two agent storage portions, a developer (not shown) composed of a magnetic carrier and a negatively chargeable toner is included. The first transport screw 5a is driven to rotate by a driving unit (not shown), thereby transporting the developer in the first agent container 5e from the front side to the back side in the drawing. And it penetrates into the 2nd agent accommodating part 5f through the communication port which is not shown in the partition wall between the 1st agent accommodating part 5e and the 2nd agent accommodating part 5f. The second transport screw 5b in the second agent container 5f is rotated by a driving means (not shown), thereby transporting the developer from the back side to the front side in the drawing. The developer concentration in the middle of conveyance is detected by a toner concentration sensor 5c fixed to the bottom of the second agent storage portion 5f. In the upper part of the second conveying screw 5b for conveying the developer in this way in the figure, a developing roll 5g that includes the magnet roller 5i in the developing sleeve 5h that is driven to rotate counterclockwise in the figure is disposed in parallel. ing. The developer conveyed by the second conveying screw 5b is pumped up to the surface of the developing sleeve 5h by the magnetic force generated by the magnet roller 5i. Then, after the layer thickness is regulated by a doctor blade 5d arranged so as to maintain a predetermined gap from the developing sleeve 5h, it is conveyed to a developing region facing the photosensitive member 2 and is electrostatically charged on the photosensitive member 2. Toner adheres to the latent image. By this adhesion, a Y toner image is formed on the photoreceptor 2. The developer that has consumed toner by the development is returned to the second conveying screw 5b as the developing sleeve 5h of the developing roll 5g rotates. And if it conveys to the near end in a figure, it will return in the 1st agent accommodating part 5e through the communication port which is not shown in figure.

  The detection result of the magnetic permeability of the developer by the toner concentration sensor 5c is sent to a control unit (not shown) as a voltage signal. Since the magnetic permeability of the developer has a correlation with the toner concentration of the developer, the toner concentration sensor 5c outputs a voltage having a value corresponding to the toner concentration. The control unit includes a RAM, in which data of Vtref, which is a target value of the output voltage from the toner density sensor 5c, is stored. For the developing unit 5, the value of the output voltage from the toner density sensor 5c is compared with Vtref, and a toner supply device (not shown) is driven for a time corresponding to the comparison result. By this driving, an appropriate amount of toner is supplied from the first agent container 5e to the developer whose toner density has been reduced by consuming the toner during development. For this reason, the toner concentration of the developer in the second agent container 5e is maintained within a predetermined range.

  The cleaning unit 3 removes untransferred toner remaining on the surface of the photoconductor 2 without being transferred from the surface of the photoconductor 2. The cleaning unit 3 is provided with a cleaning blade 3a that is a blade member that contacts the surface of the photoreceptor in the counter direction. Further, the cleaning unit 3 includes a collection unit 3b that collects the transfer residual toner on the surface of the photoreceptor 2 removed by the cleaning blade 3a. The collection unit 3b includes a conveyance auger 3c that conveys the toner collected by the collection unit to a waste toner bottle (not shown).

  Transfer residual toner on the surface of the photoreceptor 2 is removed by the cleaning blade 3a. The transfer residual toner collected at the tip of the cleaning blade 3a falls to the collection unit 3b. Then, the toner is transported as waste toner to a waste toner bottle (not shown) by the transport auger 3c and stored therein. The waste toner stored in the waste toner bottle in this way is collected by a service person or the like. Note that the transfer residual toner collected in the collection unit 3b may be conveyed to the developing unit 5 as recycled toner and used again for development.

  The lubricant application unit 6 as a lubricant application means applies a lubricant to the surface of the photoreceptor 2 to reduce the coefficient of friction on the surface of the photoreceptor 2. The lubricant is applied to the surface of the photoreceptor 2 by molding the lubricant into a solid form to form a solid lubricant 6a, and pressing the solid lubricant 6a against the fur brush 6c that is rotated by the pressure spring 6b, thereby fur brush. It is applied to the photoreceptor 2 via 6c. As the lubricant, ZnSt (zinc stearate) is most commonly used. The fur brush 6c is made of insulating PET, conductive PET, acrylic fiber, or the like. The lubricant applied to the surface of the photosensitive member is fixed to the surface of the photosensitive member with a uniform thickness by the lubricant application blade 6d. By applying a lubricant to the surface of the photoconductor 2, filming of the photoconductor 2 can be prevented.

  As shown in FIG. 1, an optical writing unit 20 is disposed below the process cartridges 1Y, 1C, 1M, and 1K in the drawing. The optical writing unit 20 serving as a latent image forming unit irradiates each photoconductor in each of the process cartridges 1Y, 1C, 1M, and 1K with a laser beam L emitted based on the image information. As a result, electrostatic latent images for Y, C, M, and K are formed on the photoreceptors 2Y, 2C, 2M, and 2K. The optical writing unit 20 deflects the laser light L emitted from the light source by the polygon mirror 21 that is rotationally driven by a motor, and passes through the photosensitive members 2Y, 2C, 2M, and 2K via a plurality of optical lenses and mirrors. Is irradiated.

  A first paper feed cassette 31 and a second paper feed cassette 32 are arranged on the lower side of the optical writing unit 20 in the drawing so as to overlap in the vertical direction. In each of these paper feed cassettes, a plurality of transfer papers P as recording bodies are accommodated in a state of a bundle of transfer papers, and the first paper feed roller 31a, The second paper feed rollers 32a are in contact with each other. When the first paper feed roller 31a is driven to rotate counterclockwise in the figure by driving means (not shown), the uppermost transfer paper P in the first paper feed cassette 31 is vertically oriented on the right side of the cassette in the figure. The paper is discharged toward the paper feed path 33 arranged so as to extend. Further, when the second paper feed roller 32 a is driven to rotate counterclockwise in the figure by a driving means (not shown), the uppermost transfer paper P in the second paper feed cassette 32 is directed toward the paper feed path 33. Discharged. A plurality of transport roller pairs 34 are arranged in the paper feed path 33, and the transfer paper P sent to the paper feed path 33 is sandwiched between the rollers of the transport roller pair 34, while the paper feed path 33. 33 is conveyed from the lower side to the upper side in the figure.

  A registration roller pair 35 is disposed at the end of the paper feed path 33. The registration roller pair 35 temporarily stops the rotation of both rollers as soon as the transfer paper P sent from the transport roller pair 34 is sandwiched between the rollers. Then, the transfer paper P is sent out toward a later-described secondary transfer nip at an appropriate timing.

  Above each of the process cartridges 1Y, 1C, 1M, and 1K, there is disposed a transfer unit 40 that endlessly moves counterclockwise in the drawing while stretching an intermediate transfer belt 41 that is an intermediate transfer member. The transfer unit 40 serving as transfer means includes an intermediate transfer belt 41, a belt cleaning unit 42, a first bracket 43, a second bracket 44, and the like. Further, four primary transfer rollers 45Y, 45C, 45M, 45K, a secondary transfer backup roller 46, a drive roller 47, an auxiliary roller 48, a tension roller 49, and the like are also provided. The intermediate transfer belt 41 is endlessly moved counterclockwise in the figure by the rotational driving of the driving roller 47 while being stretched by these eight rollers. The four primary transfer rollers 45Y, 45C, 45C, 45M, 45K, and 45K sandwich the intermediate transfer belt 41 that is moved endlessly in this manner from the photoreceptors 2Y, 2C, 2M, and 2K, thereby forming primary transfer nips. ing. Then, a transfer bias having a polarity opposite to that of the toner (for example, plus) is applied to the back surface (loop inner peripheral surface) of the intermediate transfer belt 41. The intermediate transfer belt 41 sequentially passes through the primary transfer nips for Y, C, M, and K along with the endless movement thereof, and on the surface of the photoreceptor 2Y, C, M, K on the front surface. The Y, C, M, and K toner images are superimposed and primarily transferred. As a result, a four-color superimposed toner image (hereinafter referred to as a four-color toner image) is formed on the intermediate transfer belt 41.

  The secondary transfer backup roller 46 sandwiches the intermediate transfer belt 41 with the secondary transfer roller 50 disposed outside the loop of the intermediate transfer belt 41 to form a secondary transfer nip. The registration roller pair 35 described above sends the transfer paper P sandwiched between the rollers toward the secondary transfer nip at a timing at which the transfer paper P can be synchronized with the four-color toner image on the intermediate transfer belt 41. The four-color toner image on the intermediate transfer belt 41 is affected by the secondary transfer electric field formed between the secondary transfer roller 50 to which the secondary transfer bias is applied and the secondary transfer backup roller 46, and the influence of the nip pressure. The secondary transfer is batch-transferred onto the transfer paper P in the secondary transfer nip. Then, combined with the white color of the transfer paper P, a full color toner image is obtained.

  Transfer residual toner that has not been transferred to the transfer paper P adheres to the intermediate transfer belt 41 after passing through the secondary transfer nip. This is cleaned by the belt cleaning unit 42.

  A fixing unit 60 including a pressure roller 61 and a fixing belt unit 62 is disposed above the secondary transfer nip in the drawing. The fixing belt unit 62 of the fixing unit 60 moves the fixing belt 64 endlessly in the counterclockwise direction in the drawing while being stretched by the heating roller 63, the tension roller 65, and the driving roller 66. The heating roller 63 includes a heat source such as a halogen lamp, and heats the fixing belt 64 from the back side. A pressure roller 61 that is driven to rotate clockwise in the drawing is in contact with the surface of the fixing belt 64 that is heated in this manner from the front side. Thereby, a fixing nip where the pressure roller 61 and the fixing belt 64 abut is formed.

  The transfer paper P that has passed through the secondary transfer nip is separated from the intermediate transfer belt 41 and then sent into the fixing unit 60. Then, in the process of being conveyed from the lower side to the upper side in the figure while being sandwiched by the fixing nip, the full-color toner image is fixed by being heated or pressed by the fixing belt 64.

  The transfer paper P subjected to the fixing process in this way passes through between the rollers of the paper discharge roller pair 67 and is then discharged outside the apparatus. A stack unit 68 is formed on the upper surface of the housing of the printer main body, and the transfer sheets P discharged to the outside by the pair of discharge rollers 67 are sequentially stacked on the stack unit 68.

  Above the transfer unit 40, four toner cartridges 120Y, 120C, 120M, and 120K that store Y, C, M, and K toners are disposed. The Y, C, M, and K toners in the toner cartridges 120Y, 120C, 120M, and 120K are appropriately supplied to the developing units of the process cartridges 1Y, 1C, 1M, and 1K, respectively. These toner cartridges 120Y, 120C, 120M, and 120K can be attached to and detached from the printer main body independently of the process cartridges 1Y, 1C, 1M, and 1K.

  In the printer having the above-described configuration, toner image formation for forming a toner image on the transfer paper P, which is a recording medium, by combining the four process cartridges 1Y, 1C, 1M, 1K, the optical writing unit 20, the transfer unit 40, and the like. Means are configured.

  FIG. 3A is a longitudinal sectional view showing the process cartridge 1 set in the printer and its peripheral configuration. FIG. 3B shows the process cartridge 1 being removed from the printer. It is a longitudinal cross-sectional view shown with a surrounding structure. In the left and right directions of these drawings, the left side corresponds to the front side of the printer, and the right side corresponds to the rear side of the printer. As shown in FIG. 3A, the process cartridge 1, which is a unit having a rotating body and detachable from the apparatus main body, includes a front side plate 71 disposed near the front end of the printer main body, It is located between the rear side plate 70. As shown in FIG. 3B, a center hole penetrating from one end side to the other end side in the axial direction is formed at the center of the circle of the cylindrical photosensitive member 2. The rear plate 70 rotatably supports the photosensitive shaft 172 as a driven shaft by a bearing (not shown). As shown in FIG. 3A, when the process cartridge 1 is set in the printer, the photosensitive member shaft 172 supported by the rear plate 70 is placed in the central hole of the photosensitive member 2 as a rotating member. A shaft 172 is inserted. The cross-sectional shape of the center hole is a non-circular shape such as a D-shape or an oval shape, and the cross-sectional shape of the photoconductor shaft 172 is a similar shape. Thereby, the rotational driving force of the photosensitive member shaft 172 is transmitted to the photosensitive member 2Y without the photosensitive member shaft 172 inserted into the center hole spinning in the hole.

  Since the above-described photoconductor shaft 172 passes through the rear plate 70 of the printer main body, the rear end portion thereof is located further on the rear side of the rear plate 70. A driving device 80 including a bracket 82, a driving motor 81 as a driving source, a constant velocity joint 130 as a connecting means, and the like is fixed to a surface of the rear side plate 70 of the printer main body opposite to the surface facing the front side plate 70. The drive motor 81 and the photoconductor shaft 172 are aligned on a straight line, and the rotational drive force from the drive motor 81 is transmitted to the photoconductor shaft 172 via the constant velocity joint 130.

  The drive motor 81 is a so-called direct drive motor that transmits a rotational driving force to the photosensitive member 2 without using a gear or the like. By connecting the driving force between the driving shaft 81a and the photosensitive member shaft 172 without using a gear, it is possible to avoid speed fluctuations of the photosensitive member 2 due to gear eccentricity and tooth pitch unevenness.

  When removing the process cartridge 1 from the printer, the movable front plate 71 is retracted from the position facing the rear plate 70. Then, the process cartridge 1 is pulled out from the rear side of the printer toward the front side. The photosensitive member 2 is held by the frame 90 of the process cartridge 1.

  FIG. 4 is a cross-sectional view showing the driving device 80. In the figure, the left side of the rear plate 70 in the figure is the unit side in which the process cartridge 1 (not shown) is accommodated, and the right side in the figure is the drive transmission side in which the drive device 80 and the like are accommodated. The drive device 80 includes a bracket 82 fixed to the drive transmission side surface of the rear plate 70, a drive motor 81 fixed to the back surface of the bracket 82, and a constant velocity joint 130 as a connecting means housed in the bracket 82. And have.

  The bracket 82 is formed by bending a sheet metal such as press working. And it has two positioning pins 82a and 82b which are inserted in the two positioning holes 74 and 75 of the rear side plate 70, respectively, for positioning the bracket 82 on the rear side plate 70. Moreover, it has the fixing | fixed part 82c for screw-fixing to the rear side board 70. FIG. The fixing portion 82c is provided with a screw hole (not shown) for fixing the bracket 82 to the rear side plate 70 with screws.

  The drive motor 81 fixed to the back surface of the bracket 82 passes the drive shaft 81a through a round hole formed in the back surface of the bracket 82, so that the motor body is positioned outside the bracket 82 and the drive shaft 81a The tip side is located inside the bracket 82.

  The photoreceptor shaft 172 as a driven shaft passes through the rear plate 70 while being press-fitted into a bearing 73 fixed to the rear plate 70. A fixing ring 173 having a diameter larger than that of the photosensitive member shaft 172 is fitted in a predetermined position in the axial direction of the photosensitive member shaft 172, and the fixing ring 173 abuts against the side surface of the bearing 73 on the unit side, thereby The photosensitive member shaft 172 is positioned in the axial direction with respect to.

  The constant velocity joint 130 connects the drive shaft 81 a and the photosensitive member shaft 172 that are aligned in the axial direction inside the bracket 82. As described above, the bracket 82 is formed by bending a sheet metal, and variation in the bending angle is likely to occur during processing. Therefore, it is difficult to accurately position the drive motor 81 with respect to the rear plate 70. Then, the drive shaft 81 a of the drive motor 81 tends to be inclined with respect to the photosensitive member shaft 172. In this printer, even if the skew of the drive shaft 81a occurs in this manner, the drive shaft 81a and the photosensitive member shaft 172 are connected by the constant velocity joint 130, so that the drive shaft 81a is rotationally driven with respect to the photosensitive member shaft 172. It is possible to transmit force at a constant speed.

  Next, the constant velocity joint will be described with reference to FIGS.

  The constant velocity joint 130 includes an outer ring 140 and a cage 150. A photoreceptor shaft 172 is connected to the left end portion of the cage 150 in the axial direction of the drawing. A drive shaft 81a of the drive motor 81 is connected to the right end of the outer ring 140 in the axial direction in the drawing.

  The outer ring 140 includes a cylindrical cup portion 141 into which a part of the cage 150 is inserted from an opening provided on one end side in the axial direction. From the other end side of the cup part 141, a cylindrical shaft attaching part 147 protrudes so as to extend on the central axis of the cup part 141. In the cup portion, an inner boss portion 143 is provided on the central axis of the cup portion 141, and an annular space 144 is formed between the cup portion 141 and the inner boss portion 143. The cup part 141, the shaft mounting part 147, and the inner boss part 143 constituting the outer ring 140 are integrally formed (integrated molding) with the same resin material.

  The outer ring 140 has three outer grooves 145 that are three track grooves provided on the inner peripheral surface of the cup portion 141 and three inner grooves 146 that are three track grooves provided on the outer peripheral surface of the inner boss portion 143. . As shown in FIG. 4, one end side in the axial direction in the annular space 144 is opened and the other end side is closed, and the cage 150 is inserted from the opening. The drive shaft 81a is fitted and fixed in the internal space of the cylindrical shaft mounting portion 147.

  As shown in FIG. 5, the three outer grooves 145 provided on the inner circumferential surface of the cup portion 141 extend in the axial direction of the cup portion 141 and have a phase difference of 120 ° with respect to each other in the circular direction. It is formed to line up. The three inner grooves 146 provided on the outer peripheral surface of the inner boss portion 143 are also formed to extend in the axial direction of the inner boss portion 143 and to be arranged in a circular direction with a phase difference of 120 °. . The outer groove 145 and the inner groove 146 face each other through the annular space 144.

  As shown in FIG. 6, a tapered outer groove guide portion 145 a is provided on the opening end side of the outer groove 145 so as to move away from the axial center and increase in groove width toward the opening end. The opening end of the inner groove 146 is provided with a tapered inner groove guide portion 146a that approaches the axial center and increases the groove width toward the opening end. Thus, by providing the guide portions 145a and 146a, the ball 152 can be guided to the annular space 144 where the outer groove 145 and the inner groove 146 face each other, and the cage 150 can be easily inserted into the outer ring 140. be able to.

  Further, at the opening end of the cup portion 141, the edge portions of the inner groove guide portions 146a intersect. With this configuration, when the cage 150 and the outer ring 140 are assembled, even if the phase between the track groove (the outer groove 145 and the inner groove 146) and the ball 152 is around 60 °, the ball 152 is moved into the inner groove. The opening end of the guide part 146a can be contacted. Thereby, even if the phase of the ball 152 and the track groove (the inner groove 146 and the outer groove 145) is around 60 °, a part of the axial force applied to the inner boss portion 143 is caused by the inner groove guide portion 146a. The force can be converted into a rotational force, and the cage 150 can be rotated relatively smoothly with respect to the outer ring 140. Therefore, it is possible to reduce insertion resistance when the ball 152 held in the cage 150 is inserted into the annular space 144 between the outer groove 145 and the inner groove 146 of the outer ring 140, and the ball 152 can be reduced to the outer groove of the outer ring 140. 145 and the inner groove 146 can be smoothly inserted into the annular space 144.

  The distal end side of the cage 150 is a cylindrical insertion portion 151. As shown in the cross section of FIG. 7, the insertion portion 151 has three through holes 151a as three ball holding holes provided in the cylindrical peripheral wall so as to be aligned along the circumferential direction with a phase difference of 120 °. The ball 152 as a sphere is rotatably held in each through hole 151a.

  The hole diameter A of the through hole 151 a is larger than the diameter B of the ball 73. In addition, an inner peripheral retaining protrusion 151c protruding from the inner peripheral end of the inner surface of the through hole 151a is provided with a phase difference of 180 °. In addition, an outer peripheral retaining protrusion 151b protruding from the outer peripheral end of the inner surface of the through hole 151a is provided with a phase difference of 180 °. Further, the outer peripheral retaining protrusion 151b is provided with a 90 ° phase difference from the inner peripheral retaining protrusion 151c. The inscribed circle diameter C of the retaining protrusions 151b and 151c is preferably set in the range of 80 to 99% of the ball diameter. If the inscribed circle diameter C is smaller than 80% of the ball diameter, the retaining protrusions 151b and 151c protrude too much from the through hole, and the ball 152 cannot be inserted into the through hole 151a. The retaining protrusions 151b and 151c are formed by forcibly removing the mold. However, if the protrusions 151b and 151c protrude too much, the retaining protrusions 151b and 151c may be damaged when the mold is removed after injection molding. For this reason, the inscribed circle diameter C of the retaining protrusions 151 b and 151 c is preferably set to 80% or more of the diameter of the ball 152. The ball 152 in the through hole 151a does not fall off from the outer peripheral surface of the insertion portion 151 by the outer peripheral retaining protrusion 151b. Further, the ball 152 in the through hole 151a is prevented from falling off from the inner peripheral surface of the insertion portion 151 by the inner peripheral retaining protrusion 151c.

  Further, by making the hole diameter A of the through hole 151a larger than the diameter B of the ball 152, the ball 152 can be moved in the radial direction in the through hole 151a. Thereby, when the insertion part 151 of the cage 150 is inserted into the annular space of the outer ring, when the ball 152 hits the cup part 141 of the outer ring 140, the ball 152 moves in the axial center direction. Thereby, the insertion part 151 of the cage 150 can be smoothly inserted into the annular space 144 of the outer ring 140.

  Further, by making the hole diameter A of the through hole 151 a larger than the diameter B of the ball 152, the ball smoothly rotates in the through hole. Thereby, since the ball slides while rotating in the inner groove and the outer groove during driving, it is possible to suppress wear of the inner groove and the outer groove, and to ensure constant speed over a long period of time. Thereby, durability of a constant velocity joint can be improved.

  In particular, although details will be described later, it is preferable to set the diameter of the through hole to be 5 [μm] to 50 [μm], more preferably 10 [μm] to 30 [μm] larger than the diameter of the ball. . By setting in this way, high constant speed accuracy can be maintained over a long period of time.

  In FIG. 4 shown above, the cylindrical insertion portion 151 of the cage 150 is inserted into the annular space 144 in the cup portion 141 of the outer ring 140. In this state, as shown in FIG. 8, the three balls 152 held in the through hole 151 a are respectively connected to the outer groove 145 provided on the inner peripheral surface of the outer ring cup portion 141 and the outer periphery of the inner boss portion 143. It is sandwiched between inner grooves 146 provided on the surface, and movement in the normal direction is prevented. However, since the outer groove 145 and the inner groove 146 each extend in the axial direction, the movement of the ball 152 in the axial direction is allowed.

  As shown in FIG. 8, the cylindrical insertion portion 151 of the cage 150 is inserted into the annular space 144 of the cup portion 141 of the outer ring as shown in FIG. The outer groove 145 and the inner groove 146 are engaged in the annular space 144. When rotating with the drive shaft 81 a of the drive motor 81 shown in FIG. 4, the rotational driving force is transmitted to the cage 150 through the three balls 152 at a constant speed. As a result, the photosensitive member shaft 172 and, in turn, the photosensitive member (not shown) rotate at a constant speed.

  In addition, although the example which provided the track groove for engaging the ball | bowl 152 in both the inner peripheral surface of the cup part 141 and the outer peripheral surface of the inner boss | hub part 143 was demonstrated, a track groove is formed only in any one May be.

  The resin material in which the cup part 141, the shaft attaching part 147, and the inner boss part 143 shown in FIG. 4 are integrated is made of a synthetic resin that can be injection-molded. As long as injection molding is possible, either a thermoplastic resin or a thermosetting resin may be used. Synthetic resins that can be injection-molded include crystalline resins and non-crystalline resins. Any resin may be used, but it is preferable to use a crystalline resin because the amorphous resin has low toughness and abrupt destruction occurs when a torque exceeding an allowable amount is applied. Moreover, it is desirable to use one having relatively high lubrication characteristics. Such synthetic resins include polyacetal (POM), nylon, injection-moldable fluororesins (eg, PFA, FEP, ETFE, etc.), injection-moldable polyimide, polyphenylene sulfide (PPS), wholly aromatic polyester, polyether ether Examples thereof include ketone (PEEK) and polyamideimide. These synthetic resins may be used alone or as a polymer alloy in which two or more types are mixed. Moreover, even if it is a synthetic resin other than these and resin with a comparatively low lubrication characteristic, if it is set as the polymer alloy which mix | blended the synthetic resin mentioned above, it can be used.

  The most suitable synthetic resins for the cup part 141 and the like are POM, nylon, PPS, and PEEK. Nylon is nylon 6, nylon 66, nylon 610, nylon 612, nylon 11, nylon 12, nylon 46, semi-aromatic nylon having an aromatic ring in the molecular chain, or the like. Among these, POM, nylon, and PPS are excellent in heat resistance and lubricity, and are relatively inexpensive. Therefore, the constant velocity joint 130 with excellent cost performance can be realized. Moreover, PEEK is excellent in mechanical strength and lubricity even if it does not contain a reinforcing material or a lubricant, so that a high-performance constant velocity joint can be realized.

  In the constant velocity joint 130 having such a configuration, the weight of the outer ring 140 can be reduced by forming the cup portion 141 from a resin material as compared with the conventional configuration in which the cup portion 141 is formed from a metal material. . Further, since the inner peripheral surface of the cup portion 141 is made of a resin material, the outer ring 140 and the cage 150 can be smoothly rotated and formed with a metal material without filling the annular space 144 with grease. The operation sound can be reduced as compared with the above configuration. As a result, the constant velocity joint 130 in the printer can be reduced in weight, can reduce the operating noise during torque transmission, and can be dispensed with grease. As a result, noise and grease contamination are no longer restricted, making it possible to apply to office machines, audio equipment, medical equipment, household appliances, food manufacturing equipment, etc., which were difficult in the past. it can.

  In addition, it is also possible to add a solid lubricant and lubricating oil to the resin material which comprises the cup part 141 grade | etc., And to improve a lubrication characteristic. Examples of the solid lubricant include PTFE, graphite, molybdenum disulfide and the like. Moreover, glass fiber, carbon fiber, and various mineral fibers (whiskers) may be added to the resin material to increase the strength, or may be used in combination with a solid lubricant or the like.

  In the constant velocity joint of the present embodiment, as described above, the diameter of the through hole is preferably set to 10 [μm] to 30 [μm] larger than the diameter of the ball. The molding accuracy of the through hole is affected because of the cage. For this reason, detailed considerations such as molding conditions during injection molding, mold accuracy, and molding shrinkage of the synthetic resin to be used are necessary. For example, 15% by volume or more of an inorganic compounding agent may be blended with the synthetic resin to reduce the molding shrinkage rate.

  As the balls 152, bearing steel, stainless steel balls, ceramic balls, balls made of synthetic resin, or the like can be used. Of these, stainless steel balls are suitable because they are free from rusting and are inexpensive.

  In this printer, not only the outer ring 140 but also the cage 150 is made of a resin material. The resin material suitable for the cage 150 is the same as that suitable for the outer ring 140. Further weight reduction can be achieved by configuring the cage 150 with a resin material.

  In this printer, as shown in FIG. 3B, the photosensitive member 2 that rotates about the photosensitive member shaft 172 that is a driven shaft is used as a latent image carrier, and the photosensitive member shaft 172 is connected to a constant velocity joint. 130 is connected. Even if the drive shaft 81a of the drive motor 81 is skewed with respect to the photosensitive member shaft 172 due to variations in the bending accuracy of the bracket 82, the rotational driving force can be transmitted to the photosensitive member 2 at a constant speed. Is as already described. Further, as shown in FIG. 3, the photosensitive member 2 causes the photosensitive member shaft 172 to penetrate and engage with a central hole formed in the axial direction. In such a configuration, the photoconductor 2 and the process cartridge 1 can be attached to and detached from the apparatus main body with the photoconductor shaft 172 fixed to the apparatus main body side.

In FIG. 4 shown above, the outer ring 140 has a cylindrical shaft mounting portion 147 that protrudes in the axial direction from one end portion in the axial direction of the cup portion. And the outer ring | wheel 140 and the drive shaft 81a are connected to the axial direction because the drive shaft 81a of the drive motor 81 is press-fitted in the hollow space of the shaft portion 153.
One end of the photosensitive member shaft 172 has a hollow structure, and the photosensitive member shaft 172 and the cage 150 are connected by inserting the shaft portion 153 of the cage 150 into the hollow structure. In addition, a thrust pressing member 174 is fitted to one end portion of the photosensitive member shaft 172 on the outside thereof. As a result, the thrust holding member 174, the photoconductor shaft 172, and the shaft portion 153 overlap on one end side of the photoconductor shaft 172. The photosensitive member shaft 172 and the shaft portion 153 are provided with through holes (not shown) that pass through in the direction orthogonal to the axial direction. A through hole (not shown) that is orthogonal to the axial direction is also provided on a part of the circumferential surface of the hollow thrust holding member 174. Furthermore, a screw hole is provided to face this through hole through a hollow. The screw 175 is inserted into the through hole of the thrust holding member 174, the photosensitive member shaft 172, and the shaft portion 153 in a state where the respective through holes and screw holes are positioned in a straight line, and then into the screw hole of the thrust holding member 174. It is screwed together. As a result, the cage 150 is fixed to the photoreceptor shaft 172.

  As shown in the figure, the thrust holding member 174 that is a cylindrical member is sandwiched between the insertion portion 151 and the bearing 73 without a gap. This prevents the photoreceptor shaft 172 from coming off the bearing 73. As described above, in this printer, the photosensitive shaft 172 is inserted into the thrust pressing member 174 having a diameter larger than that of the photosensitive shaft 172, and the thrust pressing member 174 is positioned between the cage 150 and the bearing 73. It is possible to prevent the photoreceptor shaft 172 from coming off from the bearing 73.

Next, a method for connecting the photosensitive member shaft 172 and the drive shaft 81a will be described.
As shown in FIG. 4, the photoreceptor shaft 172 is press-fitted from a process cartridge (not shown) into a bearing 73 fixed to the rear plate 70 of the printer main body. Then, the fixing ring 173 fixed to the photosensitive member shaft 172 is abutted against the side of the process cartridge of the bearing 73, thereby positioning the photosensitive member shaft 172 in the axial direction with respect to the printer main body.

  Next, a thrust holding member 174 is inserted into one end portion penetrating from the rear plate 70 to the driving device 80 side of the photoreceptor shaft 172, and the cage shaft portion 153 is inserted into the hollow portion. A thrust holding member 174 is fixed to the photoreceptor shaft 172.

  When the photosensitive member shaft 172 is attached to the apparatus main body as described above, the drive shaft of the drive motor 81 and the outer ring attached to the drive shaft are then attached to the back surface of the bracket 82 as shown in FIG. The cage is inserted into the formed round hole, and the cage insertion portion 151 attached to the photoreceptor shaft 172 is inserted into the cup portion of the outer ring to engage the outer ring and the cage. At this time, if the phase of the ball 152 and the phase of the track grooves (inner groove 146 and outer groove 145) are different, the ball 152 is guided to the inner groove guide portion 146a and the outer groove guide portion 145a, and the drive motor The cage 150 or the outer ring 140 rotates in conjunction with the insertion operation of 81, and the phase of the ball 152 and the phase of the track grooves (the inner groove 146 and the outer groove 145) are matched. When the phases of the ball 152 and the track groove (the inner groove 146 and the outer groove 145) are matched, the insertion portion 151 of the cage 150 is inserted into the annular space of the outer ring 140, and the three balls 152 held by itself are held. The outer groove 145 and the inner groove 146 are engaged in the annular space 144. In this way, when the cage 150 and the outer ring 140 are engaged, the drive motor 81 is screwed to the bracket 82.

  Either the outer ring 140 or the cage 150 may be attached to the drive shaft 81a, but it is preferable to attach the outer ring 140 to the drive shaft 81a as shown in the figure. This is because the outer ring 140 has a larger sliding amount with respect to the ball 152 than the cage 150, so that the wear progresses faster than the cage 150, and the life is reached early. When the outer ring 140 is attached to the photoconductor shaft 172, the outer ring 140 is replaced by removing the bracket 82 from the rear plate 70 and removing it from the photoconductor shaft in the apparatus main body supported by the rear plate 70. As described above, when the outer ring 140 is attached to the photosensitive member shaft, the outer ring is removed from the inside of the apparatus main body, so that the replacement workability is poor. On the other hand, when the outer ring 140 is attached to the drive shaft 81a, the outer ring 140 can be replaced by removing the drive motor 81 from the bracket 82 and taking it out from the apparatus main body. Thus, when the outer ring 140 is attached to the drive shaft 81a, the outer ring can be exchanged outside the apparatus main body, and the workability is good. Therefore, it is easier to replace the outer ring 140 when the outer ring 140 is attached to the drive shaft 81a than when it is attached to the photosensitive member shaft. Further, the ease of maintenance can be improved when the outer ring 140 whose life is earlier than the cage 150 is attached to the drive shaft 81a than when the cage 150 is attached to the drive shaft 81a.

Next, a characteristic configuration of the printer according to the present embodiment will be described based on Experiments 1 and 2.
[Experiment 1]
In Experiment 1, six constant velocity joints with different fitting clearances between the ball and the through hole (hole diameter of the through hole−ball diameter) were prepared. Under the experimental conditions shown below, the amount of wear, the constant velocity accuracy, Was investigated. The constant velocity joint used in the experiment was made of SUS304, a ball having a diameter of 6 mm, an outer ring made of PPS (containing 15% by volume of carbon fiber), and a material made of PPS (containing 15% by volume of carbon fiber). A cage was used.
[Experimental conditions]
Operation time: 200 hours (1 Cycle (forward rotation 5 hours → pause → reverse rotation 5 hours → pause) × 20 Cycle)
Rotation speed: 100rpm
Amount of wear: change in outer ring mass (outer ring mass before start of operation-outer ring mass after 200 hours of operation)
Constant speed accuracy: driven deviation from drive by speed deviation frequency analysis of drive-driven difference (◎: driven deviation 0.03% or less, ○: driven deviation 0.1% or less, Δ: driven deviation 0.2% or less, × : Followed deviation 0.2% or more)

As shown in Table 1, in the constant velocity joint with zero fitting gap, the wear amount after 200 hours is 40 [mg], and it can be seen that the track grooves are considerably worn. As a result, the constant velocity accuracy after 200 hours becomes x, and it can be seen that the constant velocity property cannot be maintained for a long time. Further, in a constant velocity joint having a fitting gap of 110 [μm], sufficient constant velocity accuracy was not obtained from the initial use. It is considered that this is because the fitting gap is too large, and the ball rattles in the through hole during driving, and the constant velocity cannot be maintained.
On the other hand, in a constant velocity joint having a fitting gap of 5 [μm] or more and 50 [μm] or less, good constant velocity accuracy was ensured at the initial stage and after 200 hours of operation. In particular, in a constant velocity joint with a fitting gap of 10 [μm] or more and 30 [μm] or less, the wear amount can be suppressed to 1 [mg] or less, and the constant velocity can be maintained over a long period of time. . Note that the amount of wear increases as the fitting gap increases for the following reason. When the through hole of the cage hits the ball at the start of driving, the impact increases as the fitting gap increases. The track groove is worn by the impact at the start of driving. Therefore, it is considered that the wear amount increases as the fitting gap increases.

[Experiment 2]
In Experiment 2, an experiment similar to Experiment 1 was performed using a constant velocity joint with a ball diameter of 8 mm. That is, the constant velocity joint used in the experiment is made of SUS304 material, a ball having a diameter of 8 [mm], an outer ring made of PPS (carbon fiber 15% by volume), and made of PPS (carbon fiber 15% by volume). (Combination) cage.
The experimental results at this time are shown in Table 2.

  As shown in Table 2, even in the constant velocity joint having a ball diameter larger than that in Experiment 1, when the fitting gap was 0, the inner groove and the outer groove were worn as in Experiment 1, and after 200 hours. The constant speed accuracy has become x. On the other hand, in a constant velocity joint having a fitting gap of 5 [μm] or more and 50 [μm] or less, good constant velocity accuracy after 200 hours could be secured. In particular, in a constant velocity joint with a fitting gap of 10 [μm] or more and 30 [μm], the wear amount could be suppressed to 1 [mg] or less.

  Further, as shown in FIG. 10, an outer ring 140 is attached to a photosensitive shaft 172 that is integrated with the process cartridge 1 that is a unit that can be attached to and detached from the apparatus main body, and is attached to the apparatus main body. The outer ring 140 and the cage 150 may be engaged by attaching the cage 150 to the 81a and attaching the process cartridge 1 to the apparatus main body.

FIG. 11A is a schematic configuration diagram showing the periphery of the constant velocity joint 130 before the process cartridge 1 is mounted on the printer body, and FIG. 11B is a constant velocity when the process cartridge 1 is mounted on the printer body. 3 is a schematic configuration diagram showing the periphery of a joint 130. FIG.
With the front plate 71 (not shown) of the apparatus main body opened, the process cartridge 1 is inserted into the printer main body, and a guide extending from the rear plate 70 into the guide hole 90a of the process cartridge 1 as shown in FIG. The pin 76 is inserted. When the process cartridge 1 is inserted into the apparatus main body with the guide pin 76 inserted into the guide hole 90a, the process cartridge 1 is brought into a position where the outer ring 140 can be engaged with the cage 150 by the guide pin 76. Guided.

  Then, the insertion portion 151 of the cage 150 is inserted into the annular space of the outer ring 140. At this time, if the phase of the ball 152 and the phase of the track groove (the inner groove 146 and the outer groove 145) are different, the ball 152 is guided to the inner groove guide portion 146a and the outer groove guide portion 145a, and the process cartridge The cage 150 or the outer ring 140 rotates in conjunction with the movement of 1 in the insertion direction, and the phase of the ball 152 and the phase of the track grooves (the inner groove 146 and the outer groove 145) are matched.

  When the phases of the ball 152 and the track grooves (the inner groove 146 and the outer groove 145) are matched, the insertion portion 151 of the cage 150 is inserted into the annular space of the outer ring 140, and the three balls 152 held by itself are held. The outer groove 145 and the inner groove 146 are engaged in the annular space 144. Thereby, the process cartridge 1 is positioned in the radial direction with respect to the apparatus main body, and the process cartridge 1 is mounted in the apparatus main body.

  Since the photoconductor shaft 172 of the photoconductor 2 is used as a main reference for positioning the process cartridge 1 with respect to the apparatus main body, there is no axial misalignment between the photoconductor shaft 172 and the drive shaft 81a. However, for example, when the rear plate 70 is inclined and attached to the apparatus due to an assembly error or a manufacturing error, the drive shaft 81a is inclined, and a declination is generated between the drive shaft 81a and the photosensitive member shaft 172. End up.

  However, by using the constant velocity joint 130 to connect the drive shaft 81a and the photosensitive member shaft 172, the ball 152 can be moved to the outer ring 140 even if a declination occurs between the drive shaft 81a and the photosensitive member shaft 172. By sliding in the annular space between the outer groove 145 and the inner groove 146 in the axial direction, the photosensitive member shaft 172 can be rotated at a constant speed even if there is a declination. As a result, the photosensitive member 2 can be driven to rotate at a constant speed without increasing the mounting accuracy and the component accuracy so that the declination angle θ does not occur between the drive shaft 81a and the photosensitive member shaft 172. Abnormal images such as unevenness can be suppressed. Therefore, it is possible to suppress abnormal images such as density unevenness while suppressing manufacturing costs and component costs.

  The constant velocity joint 130 is composed of three parts: an outer ring 140, a cage 150, and a ball 152. Therefore, the constant speed rotation of the photosensitive member shaft 172 and the connection between the photosensitive member shaft 172 and the drive shaft 81a can be performed with a small number of parts, and the cost of the apparatus can be reduced.

  Further, when the constant velocity joint 130 is used to connect the detachable unit and the driving device, it is preferable to attach the outer ring 140 to the driven shaft of the unit. With this configuration, the outer ring 140 having a life longer than that of the cage 150 can be easily removed from the apparatus main body together with the process cartridge 1. Thereby, replacement | exchange of an outer ring | wheel can be performed easily and maintenance property can be improved.

  Further, a connecting means between the developing roller shaft and the driving shaft of the developing unit detachable from the apparatus main body, a connecting means between the fixing roller shaft and the driving shaft of the fixing unit detachable from the apparatus main body, and the apparatus main body. For connecting the secondary transfer roller shaft and the drive shaft of the secondary intermediate transfer unit that can be attached and detached, and for connecting the drive roller shaft and the drive shaft of the intermediate transfer unit that can be attached to and detached from the apparatus body. The constant velocity joint of the present invention can be applied.

  In addition, as shown in FIG. 12, the present invention is also applied to a color image forming apparatus using a drum-shaped intermediate transfer body 141 instead of the intermediate transfer belt 41 in the electrophotographic color image forming apparatus of the intermediate transfer tandem method. be able to. As shown in FIG. 13, the present invention can also be applied to a direct transfer tandem color image forming apparatus. Further, as shown in FIG. 14, one process cartridge 1 as described above is provided, and an image is formed on the photosensitive member 2 of the process cartridge 1, and the image is transferred by the transfer roller 50 to form an image on the recording material. The present invention can also be applied to a direct transfer type monochrome image forming apparatus for recording.

As mentioned above, according to the constant velocity joint of this embodiment, since the hole diameter of the through-hole 151a which is a ball holding hole is made larger than the diameter of the ball 152, the through-hole 151a and the ball 152 do not contact, The through hole 151 a does not hinder the rotation of the ball 152. As a result, the ball 152 can be smoothly rotated, and the ball 152 can slide along the track groove while rotating. As a result, it is possible to suppress wear of the track groove, and to prevent the track groove from being uneven due to wear. As a result, the ball 152 can smoothly slide in the track groove over a long period of time, and constant velocity can be maintained over a long period of time.
Further, the through hole 151 a and the ball 152 are not in contact with each other, and the through hole 151 a does not hinder the movement of the ball 152 in the radial direction. Therefore, when the ball 152 is inserted into the annular space 144 between the track groove, the phase of the ball 152 and the track groove is shifted in the radial direction, so that the ball 152 has an open end or inner end of the outer wall surface of the annular space 144. The ball 152 smoothly moves in the radial direction even if it comes into contact with the open end of the wall surface. Accordingly, the radial phases of the balls 152 and the track grooves can be matched without strongly pushing the cage 150 toward the outer ring 140, and the cage 150 can be smoothly assembled to the outer ring 140.

  In addition, by making the hole diameter of the through hole 151a larger than the diameter of the ball by 5 [μm] or more and 50 [μm] or less, the constant speed accuracy can be maintained over a long period.

  Furthermore, by increasing the hole diameter of the through hole 151a by 10 [μm] or more and 30 [μm] or less than the diameter of the ball, wear of the track groove can be further suppressed.

  Further, it is used as a connecting means for connecting a driven shaft of a process cartridge as a unit to which the above-described constant velocity joint can be attached and detached and a driving shaft that receives a driving force from a driving source provided in the apparatus main body and rotates. Thereby, even if a declination occurs between the driven shaft and the driving shaft, the driven shaft can be rotated at a constant speed, and a good image free from density unevenness can be obtained.

1 is a schematic configuration diagram illustrating a printer according to an embodiment. FIG. 3 is an enlarged configuration diagram showing a process cartridge. (A) is a longitudinal cross-sectional view showing a process cartridge set in the printer and its peripheral configuration, and (b) is a vertical cross-sectional view showing a process cartridge being removed from the printer together with its peripheral configuration. An axial sectional view of a constant velocity joint. The cross-sectional view which shows the cup part of an outer ring | wheel. The figure which shows the cup part of an outer ring | wheel. The cross-sectional view which shows the spherical body holding | maintenance part of a cage. FIG. 5 is a cross-sectional view of the constant velocity joint shown in FIG. 4. The side view which shows the drive motor which is going to be fixed to a bracket, with a cup part engaged with an insertion part. The principal part schematic block diagram of embodiment using the constant velocity joint for the connection of a drive device and a process cartridge. (A) is a schematic block diagram showing the periphery of the constant velocity joint before the process cartridge is mounted on the printer body, and (b) shows the periphery of the constant velocity joint when the process cartridge is mounted on the printer body. FIG. The figure which shows the tandem type color image forming apparatus of a direct transfer system. 1 is a diagram illustrating an intermediate transfer type tandem color image forming apparatus using an intermediate transfer drum. FIG. The figure which shows a monochrome image forming apparatus.

Explanation of symbols

1Y, C, M, K: Process cartridge 2Y, C, M, K: Photoconductor 80: Drive device 81: Drive motor 82: Bracket 90: Frame body 130: Constant velocity joint 140: Outer ring 141: Cup portion 143: Inner Boss portion 144: annular space 145: outer groove 146: inner groove 150: cage 151: insertion portion 152: ball 153: shaft portion 172: photoconductor shaft 173: fixing ring 174: thrust holding member

Claims (4)

An outer ring having an annular space having one end opened, and having an axially extending track groove formed in plural at equal intervals in the circumferential direction on at least one of an outer wall surface and an inner wall surface of the annular space;
A cage having a ball holding hole for holding a ball sliding along the track groove;
The outer ring and / or cage is molded of synthetic resin;
A part of the cage is inserted into the annular space, and the ball held by the cage is engaged with the track groove, and either one of the cage and the outer ring is rotated via the ball. In a constant velocity joint that transmits force to the other,
A constant velocity joint, wherein a diameter of the ball holding hole is larger than a diameter of the ball. The constant velocity joint of claim 1,
A constant velocity joint, wherein a diameter of the ball holding hole is larger than the diameter of the ball by 5 [μm] or more and 50 [μm] or less. The constant velocity joint of claim 1,
The constant velocity joint, wherein a diameter of the ball holding hole is larger than the diameter of the ball by 10 [μm] or more and 30 [μm] or less. A unit having a rotating body and detachable from the apparatus body;
A connecting means for connecting a driven shaft provided in the unit for transmitting a driving force to the rotating body and a driving shaft which receives a driving force from a driving source provided in the apparatus main body and is driven to rotate; In the image forming apparatus,
An image forming apparatus using the constant velocity joint according to claim 1 as the connecting means.

Images